The present invention is an automated or self-threading tape feeder device for presentation of parts to a pickup location for subsequent retrieval and soldering or similar attachment to a substrate using a pick and place assembly machine such as Panasonic MPA or a Fuji IP pick and place PCB assembly machine. Component tape used in tape and reel feeding equipment typically comprises a embossed plastic, paper, or similar strip having cavities at regular intervals (tape pitch) containing the part to be mounted on the substrate and a second, plastic cover tape or strip sealed with adhesive (PSA) or heat to the pocket tape in such a manner as to cover the cavity in order to retain the parts therein during transport and use. Such tapes are generally of a limited length that is determined by the size of the components and the diameter of the component reel that supplies the component tape to the feeder. However, this invention relates to a tape feeder device that can feed such component tapes in a variety of formats, wherein the feeder incorporates certain functions and features that enable uninterrupted feeding during the automated changeover of a depleted reel of components with a full reel on the feeding apparatus. Previously this was accomplished via a cumbersome and time consuming process whereby the operator was required to splice the lead edge of the new tape to the trail edge of the previous tape or more commonly remove the feeding mechanism and manually thread the cover tape in and throughout the cover tape peel and take-up mechanism.
Accordingly, the invention further enables one-hand loading of tape reels (or the automated loading of reels with a robotic gantry or similar automated device). Such features enable rapid part replenishment and a minimization or elimination of production down-time experienced in the use of conventional component tape feeders on a circuit board assembly line. The preferred method for automated construction of circuit boards requires the use of high speed pick and place machines that pick components from a pickup location on a feeder and place them at predefined locations on a printed circuit board for subsequent attachment. Normally, the cover tape is peeled back from the component tape at a point just prior to the pickup location as the tape is advanced. This is done for two reasons: (1) to minimize the risk that a component will be dislodged from its pocket or depression before it is retrieved at the pick station; and (2) to eliminate the possibility of contamination. Thus, prior feeder designs have focused on ways in which to combine cover tape peel back, tape advancement, and component presentation mechanisms, sensors and other devices in a relatively compact area immediately adjacent, or in close proximity, to the pickup location.
On the other hand, the present invention takes an entirely new approach to the presentation of component reels in order to provide an automatic loading or self-threading feeder. Furthermore, the feeder design described herein also reduces the complexity of part sensing and presentation, as well as avoiding the need to incorporate numerous functional elements of the feeder in direct proximity of the pickup point. For example, the present invention moves the cover tape peeling function and the component tape drive to locations that are well “upstream” from the pickup location so as to avoid disturbing the components at the pickup location.
Moreover, a feeder produced in accordance with the present invention overcomes erratic tape motion problems associated with sprocket or tooth driven tape feeders. The present feeder does not rely on the engagement and disengagement of a tooth within a component tape drive hole for advancement of the tape. Part stability within the open pocket is compromised when the drive tooth is withdrawn, under pressure, from the corresponding drive hole in the tape. A preferred method incorporates a constant drive to the tape via a friction or traction drive method which results in a more laminar component tape motion profile. Another important objective of the present invention is to incorporate logic that makes it possible to dismount an empty component reel well before the last part has been taken from the component tape currently in the feeder and automatically load up the full reel of parts without interruption to the assembly process.
Heretofore, of the following patent has disclosed automatic threading of film, the relevant portions of which may be briefly summarized as follows:
U.S. Pat. No. 3,993,404, “SELF-THREADING MOTION PICTURE PROJECTOR,” issued to Kalart Victor Corp. on Nov. 23, 1976 teaches a means to place a film projecting apparatus in a mode to accommodate the insertion of the film into the transport.
In accordance with the present invention, there is provided automatic and bi-modal operation whereby the tape advance function and tape load function are discrete but concurrent elements of the tape transport system within a feeder.
In accordance with another aspect of the present invention, there is provided an auto-loading component tape feeding apparatus, for feeding a component tape having a plurality of pockets with components held therein by a cover tape, the component tape feeder comprising: a retractable cover tape peeling edge, station for removing and pulling a cover tape from an upper surface of the component tape; a cover tape collection station; and a component pickup location where said component tape is, upon inserting a lead edge of component tape into the auto-loading component tape feeding apparatus, automatically advanced by a drive means in contact with the component tape.
In accordance with yet another aspect of the present invention, there is provided an auto-loading component tape feeding apparatus, for feeding a component tape having a plurality of pockets with components held therein by a cover tape, the component tape feeder comprising: means for supporting a reel of component tape having components disposed within pockets in the component tape, the components being held therein by a cover tape; a cover tape peeling station where the cover tape is peeled from a surface of the component tape; a cover tape collection means, suitable for the disposition of peeled cover tape; a guide for guiding said component tape from said component tape reel support to said cover tape peeling station; a component pickup station; at least one component tape drive mechanism for frictionally engaging a surface of the component tape and advancing the component tape from a location in proximity to the cover tape peeling station and toward said component pickup station; and an open pocket transport region, disposed between said cover tape peeling station and said pick station, where said component tape is advanced by a drive means in contact with a surface thereof over at least a portion of the region where the component tape pockets are uncovered.
In accordance with yet a further aspect of the present invention, there is provided a method of operating a component tape feeder in an auto-loading mode, comprising the steps of: detecting the insertion of a component tape into a tape guide; in response to detecting the insertion of the component tape, automatically advancing, with a first component tape drive nip, the component tape to a cover tape peel position; automatically initiating the peeling of a cover tape from the surface of the component tape to expose components therein; automatically advancing the component tape to a second tape drive nip; detecting the spacing of pockets in the component tape and the presence of components in the pockets; and automatically advancing the component tape to a pickup location, where a first pocket having a component present therein is positioned at the pickup location for retrieval.
In accordance with another aspect of the present invention, there is provided a method of operating an auto-loading component tape feeder to automatically calculate the component tape pitch of a component tape in the feeder, comprising the steps of: advancing the component tape under the control of a frictional drive, said drive being driven by a stepper motor where each step is known to correspond to a particular linear displacement of the component tape; while advancing the component tape, monitoring a sensor capable of detecting the presence of a repeatable feature of the component tape at a spacing equivalent to the pitch of the component tape; and in response to the detection of a first and subsequent repeatable feature by the sensor, determining the intervening linear displacement of the component tape by the frictional drive in order to automatically calculate the component tape pitch.
One aspect of the invention is based on the discovery of techniques for the detection and advancing of components in a pocket tape, as well as the transport of components in an opened pocket tape configuration, and a technique to automatically calculate the pitch or distance between pockets. The techniques allow for the reliable and continuous tape advancement, cover tape removal and precise positioning of component tape, and more particularly the automated threading and loading of such tape.
The techniques can be implemented with a machine that is designed to fit within the form and space constraints of traditional feeders. A machine implementing the invention can include an improved cover tape collection means (e.g., reservoir, reel, downward discharge), a surrogate component cover (stationary, movable or driven), control logic and one or more drive mechanisms to reliably position components within the tape at a pickup location, etc.
The techniques described herein are advantageous because they are both efficient and practical compared to other approaches. As a result of the various aspects of the present invention, component tape feeders may be made to be auto-loading, while assuring the continued and reliable presentation of component parts at a pickup location. As a further result of the improved tape drive aspects of the present invention, it is anticipated that the motion of the component tape will be improved over the somewhat discontinuous motion that is characteristic of conventional sprocket or tooth-driven tape feeders.
The present invention will be described in connection with a preferred embodiment, however, it will be understood that there is no intent to limit the invention to the embodiment described. On the contrary, the intent is to cover all alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.